1. Field of the Invention
The present invention relates generally to a thin film transistor, a manufacturing method thereof, and a manufacturing method of an organic light emitting diode (OLED) display including the same, and provides a method capable of minimizing element defects by attaining arc prevention by performing a Joule-heating-based crystallization process using application of an electric field through a gate electrode metal and capable of improving production yield in an effective manner.
2. Description of the Related Art
In general, there are various heat treatment methods, including furnace annealing using a heat treating furnace, rapid thermal annealing (RTA) using radiant heat of a halogen lamp or the like, laser annealing using a laser, a heat treatment method using Joule heating, etc. These heat treatment methods are selected as appropriate for characteristics of materials and processes according to a temperature range of the heat treatment, uniformity of the heat treatment temperature, rate of temperature rise, cooling rate, purchase price, cost of maintenance, etc. Particularly, in cases where a high-temperature heat treatment is required or a high-speed heat treatment on a local area of a material is necessary due to the characteristics of the material and a process, selectable heat treatment methods are fairly limited.
Among the above-mentioned heat treatment methods, the laser annealing method is capable of a high-speed heat treatment on a surface of a material. However, since a determination as to whether or not a heat treatment is possible or not is made according to the wavelength of the laser and the kinds of materials requiring the heat treatment, materials on which the heat treatment can be performed is limited. Particularly, in the case of performing a heat treatment on a large area, since scanning should be performed by overlapping line beam types of lasers with each other, problems, such as non-uniformity of laser beam intensities, non-uniformity of an irradiation amount of a laser beam with time, etc., occur. Also, there is a drawback in that not only the cost of equipment, but also the cost of maintenance, are very high.
The RTA method is widely used in semiconductor manufacturing processes. However, it is applicable only to silicon wafers having a diameter of 300 mm in current technology, and it has a limit in performing a uniform heat treatment on substrates larger than that. Also, the maximum rate of temperature rise of the heat treatment is 400° C./sec, and thus the RTA method cannot be used in a process requiring a rate of temperature rise larger than 400° C./sec.
Therefore, much research on heat treatment methods capable of solving the problems and breaking free from restrictions of processes has been conducted. Among the methods, there is a high-speed heat treatment method in which Joule heating is performed by applying an electric field to a conductive layer. The heat treatment method can rapidly and selectively heat-treat a desired material by heat conduction of generated high heat, and can be expected to have a rate of temperature rise higher than the rate of temperature rise of an RTA process. However, the process has a drawback in that the process becomes complicated since a metal film for applying an electric field should be additionally formed.
The above information disclosed in this Background section is only for enhancement of an understanding of the background of the described technology, and therefore it may contain information which does not form the prior art which is already known in this country to a person of ordinary skill in the art.